How to find IP address of a machine on network?

[Derek Broughton]

Matthew Flaschen wrote:

> Derek Broughton wrote:
>> Matthew Flaschen wrote:
>> 
>>> Thomas Kaiser wrote:
>>>> You can use nmap in a terminal to scan the network for open ports.
>>>>
>>>> thomas at AMD64:~$ nmap 192.168.0.*
>>> Port-scanning doesn't tell him which computer has which IP, only that
>>> there are several computers, each with /an/ IP.  He said, "there are a
>>> few devices which get their address by DHCP".
>> 
>> I'm not seeing the difference here - nmap certainly shows all the
>> computers on my local network, with names (if we know them) and IPs - and
>> all of them got their address by DHCP, so why do you think it won't tell
>> which computer has which IP?
> 
> If it says:
> 
> Interesting ports on 192.168.0.11:
> Not shown: 1712 filtered ports
> PORT    STATE SERVICE
> 80/tcp  open  http
> 443/tcp open  https
> 
> Interesting ports on 192.168.0.17:
> Not shown: 1712 filtered ports
> PORT    STATE SERVICE
> 80/tcp  open  http
> 443/tcp open  https
> 
> how does that allow him to figure out which computer is which?
> 
Ah.  OK, I see your point - it's just a matter of options:

> $ sudo nmap -sP 192.168.0.1/23
> 
> Starting Nmap 4.62 ( http://nmap.org ) at 2009-01-16 23:53 AST
> Host 192.168.0.1 appears to be up.
> Host 192.168.0.3 appears to be up.
> Host 192.168.1.1 appears to be up.
> MAC Address: 00:13:10:9F:68:2B (Cisco-Linksys)
> Host 192.168.1.2 appears to be up.
> MAC Address: 00:13:10:9F:68:25 (Cisco-Linksys)
> Host bella.pointerstop.ca (192.168.1.101) appears to be up.
> Host Wii.pointerstop.ca (192.168.1.102) appears to be up.
> MAC Address: 00:1E:A9:8E:DC:CB (Nintendo Co.)
> Nmap done: 512 IP addresses (5 hosts up) scanned in 8.073 seconds


Shows all three routers (192.168.0.3 took a little thought - it's the 
_external_ address of the wifi router at 192.168.1.1),  my current machine 
and the neighbour's Wii (he should be in bed by now!)